External Organisations

1)This study is aimed at analysing the likely route and extent of human exposure to carbon nanotubes (CNTs) via inhalation for a set of representative CNT-containing products in a lifecycle perspective.
2)The study has been conducted by the Safety of nanomaterial Interdisciplinary Research Centre (SnIRC), led for this study by the Food and Environment Research Agency, with participation of other Academic and Industrial Experts.
3)As part of the study, a review of all available CNT-containing products was carried out, and a representative subset of the products was identified for exposure analysis. The three CNT-containing products selected for the study included lithium-ion batteries, epoxy adhesive resins, and textiles.
4)The study assessed the suitability of current lifecycle assessment (LCA) protocols for assessing inhalation exposure from CNT and other nano-products. The relevance and adequacy of the relevant ISO protocols was assessed in relation to nanotechnology products (especially CNT-containing products), and any inadequacies have been highlighted.
5)The study also analysed the possibility of exposure to CNTs arising via inhalation during all stages of the life cycles of the selected study products.
6)The findings of the study indicate that:
6a)LCA is not a tool for exposure assessment. On the contrary, exposure assessments can provide information to LCA that is relevant for impact assessment of CNT releases. LCA is, however, useful in identifying the stages in the lifecycle during which exposure may be relevant.
6b)There is an almost complete lack of data to enable both a full-scale LCA, or a quantitative exposure assessment. Due to unavailability of the required data, a simplified LCA approach is adopted in this study, focusing on the potential inhalation exposure during the lifecycle of the selected CNT-containing products. Also, the exposure assessment is limited to qualitative analysis because of the lack of data necessary for a quantitative assessment.
7)Both LCA and exposure analysis have shown that the material synthesis stage (both for CNT materials, and CNT-containing products) is prone to giving rise to inhalation exposure to CNTs. However, the few studies carried out so far have generally shown that nanoparticle emissions during synthesis can be effectively controlled through appropriate engineering measures. Significant inhalation exposure to CNT material at this stage should be preventable provided such processes are carried out under appropriate emission control and waste management procedures. The main emphasis from the exposure point of view, therefore, needs to be on other stages/ processes in the lifecycle of products, where any sophisticated emission control measures are not likely to exist, e.g. during handling, transportation, accidental release, and use and disposal of the relevant materials and products.
8)Using the currently available level of scientific evidence, those stages in the lifecycle of each study product have been highlighted where inhalation exposure to CNT is possible.
9)In brief, the study has indicated that during post-production lifecycle stages:
9a)CNT-containing batteries will carry a risk of inhalation exposure during use only if the batteries are physically cut open. The main likelihood of exposure exists during accidental release (e.g. fire), and during recycling and disposal stages. People likely to be exposed will be those working at the recycling or waste disposal premises, or in the immediate vicinity.
9b)The use of the textiles, to which CNT is added on the outer surface of the yarn in a post-production coating process, is likely to pose a greater potential for exposure to CNT than any of the other processes studied. This is the only case where a significant consumer exposure during use stage seems plausible. Other lifecycle stages where there is a likelihood of exposure include recycling (shredding and milling of worn-out textiles), and disposal through incomplete incineration. Thus those likely to be exposed would include those working at the recycling or waste disposal premises, or in the immediate vicinity.
9c)CNT-containing epoxy adhesive resins may carry a risk of inhalation exposure during use only if there are conditions that lead to formation of aerosols. The main likelihood of exposure will be during disposal through incomplete incineration. It is also of note that epoxy resins generally have a relatively short shelf life (9 months in the case of the study product). There is therefore a need to develop a mechanism for appropriate disposal of the unused (unhardened, liquid) epoxy resin for appropriate disposal.
10)Common to all the three product types studied is the need for mechanisms for appropriate end-of-life treatments (e.g. separate collection of (spent) CNT-containing batteries, recycling of CNT-containing batteries and textiles under controlled conditions, and processes that ensure complete incineration of CNT in the disposed of products).
11)Urgent research is needed to address the almost total lack of exposure data for CNT-containing consumer products, and the appropriateness of end-of-life treatments. The findings of the research would also enable the manufacturers to develop safer products through better designs that are aimed at minimising the likelihood of exposure to CNTs (and/ or other nanomaterials) during subsequent stages in the lifecycle.